This invention relates in general to needle-less hypodermic drug delivery instruments using jet injection, and in particular to such instruments that are spring actuated.
This invention is a spring powered hypodermic delivery system using the well known jet injection principal to pass liquids such as medication through skin without the use of needles. This invention does not have these disadvantages.
Over a period of many years a variety of spring powered jet injectors have been proposed and patented, but they have all met with very limited acceptance due to such disadvantages as high cost and user inconvenience. In most cases these devices have incorporated means of cocking the power spring as an integral part of the primary instrument. The mechanism involved with the cocking function increases the size and cost of these instruments and has a negative effect on the convenience of application.
In the U.S. Pat. No. 4,874,367 by Edwards, the inventor proposes the elimination of the cocking mechanism on the instrument by relying on the user to reset the spring by simply pressing the exposed ram rod against a surface such as a table top, to force the ram into the cocked position. Edwards further suggests the use of a spring having a force of 20 pounds at full compression.
Such an instrument would have extremely limited application if any. In the first place, practical experience accumulated over several decades by a number of workers in the field of jet injection, clearly indicates the need for much higher spring tensions to accommodate the wide variations in human skin thickness, dose sizes and types of medication. Secondly, higher spring forces would render the manual cocking procedure quite impractical for most individuals. Even a 20 pound spring would eliminate most children and elderly persons from using the instrument. These population segments are the primary beneficiaries of jet injection.
The invention disclosed herewith separates the spring cocking function from the injector instrument but provides an effective spring compression mechanism in a companion carrying case. The carrying case serves as a protective enclosure for the injector and at the same time automatically cocks the instrument when the lid of the case is closed. After closing the lid the injector remains in the case until needed, at which time the lid is opened and the instrument removed. It will then automatically be in the cocked condition and with an interlocking safety on.
The power unit of the system has a spring driven rod, which slides into a disposable medication ampule and forces the liquid through a small orifice to make the injection. If the trigger were actuated with the ampule not in place, the rod could inflict serious injury to the operator. This eventuality is rendered impossible by the provision of an interlock mechanism between the ampule attachment point and the injector trigger. This mechanism inserts a mechanical block under the trigger unless the ampule is in place and fully seated, thus preventing the inadvertent release of the rod.
A second level of safety is also provided at the discretion of the user. This second safety feature is engaged by moving a sliding sleeve forward, which also restricts the actuation of the trigger when the ampule is in place but the user does not wish to make the injection immediately. Both of these safety features are mandatory if the system is to be acceptable to the medical profession.
This system is dramatically smaller than conventional jet injectors, and can be as small as 33/4 inches long by 5/8 of an inch in diameter. Its cost to a user is correspondingly lower, e.g. one-tenth or less the cost of conventional instruments. For user comfort it incorporates means for adjusting penetration depth. Moreover, its simplicity is enhanced because it does not incorporate typically bulky means for resetting the instrument as an integral part. This function is accomplished by a separate component which is the subject of a related patent application. This separation helps account for the extreme simplicity of the injector and its small size.
This system comprises both permanent and disposable components cooperating in a novel design having simplicity in both structure and function resulting in low user costs.
This system is very suitable for the administration of a wide variety of drugs in clinical settings or in physicians' offices when a subcutaneous or shallow I.M. shot is appropriate. A primary application, however, is the self-administration of insulin by diabetics for which use this system is well suited.